ntific fact. But when a theory has been
raised to such a level of probability as this, it is, for all practical
purposes, as good as a demonstration. Thus, in the particular instance
before us, even if the sceptical demand for evidence, which from the
nature of the case is clearly impossible, were granted, and if we could
actually observe the transmutation of species, the fact would not exert
any further influence on the progress of science than is now exerted by
the large and converging bodies of evidence which leave no other
rational theory open to us than that such transmutation has taken place.
Therefore, it seems to me, the hypercritical objection which we are
considering is really founded on a misconception of scientific method,
and of what it is that justifies a scientific doctrine. Assuredly, in
the case of every theory, as distinguished from a demonstration, there
must always be a proportion between the evidence of and the warrant for
the proposition which the theory states; and if gauged by this simple
rule the warrant for accepting the theory of evolution is now estimated
by the judgment of all scientifically trained minds as so high, that by
no additional evidence could it be placed higher without becoming a full
demonstration. Or, otherwise stated, as a theory the doctrine of descent
is now in the topmost position of probability, so that by no amount of
additional evidence could it be raised higher without ceasing to be a
probability and becoming a certainty. That is to say, we do not need any
more evidence in any of the lines of evidence to add to the strength of
our belief in, as distinguished from our knowledge of, the truth of
evolution. For the strength of our conviction could not be increased by
the discovery of any additional number of connecting links among fossil
species, further facts relating to geographical distribution, to
morphology, classification, embryology, or any of the other lines of
evidence which have been mentioned; no further evidence the same in kind
is now competent to raise in degree the probability which has already
been raised, as far as from its very nature as a probability it can be
raised.

I have no doubt, however, that the principal obstacle which the doctrine
of evolution encounters in the popular mind is not one of reason, but of
sentiment. It is thought that the conception of man being a lineal
descendant of the monkey is a conception which is degrading to the
dignity of